Actuator for bucky diaphragms

ABSTRACT

Actuator for moving a diaphragm grid over photographic film during an X-ray exposure to screen secondary radiations from the film, comprising a drive shaft having thereon a pair of coextensive intersecting helical grooves of opposite hand which merge at their ends to form an endless track, a follower on the grid engaged in said track, and means for rotating said shaft for reciprocating said follower along said track thereby to move said grid over the film.

United States Patent Pearson et al. [45] May 2, 1972 [54] ACTUATOR FOR BUCKY 2,467,592 4/1949 Morgan et al ..250/63 D G S 2,767,323 10/1956 Stava et al. ..250/62 [72] Inventors: John R. Pearson, Aurora; Glenn J. John- Primary Examiner-James W. Lawrence son, Oswego, both of III. Assistant Examiner-A. L. Birch Assigneez Menquist g Inc. Aurora 1. Attorney-Gary, Parker, Juettner, Pigott & Cullinan [22] Filed: Mar. 21, 1969 BSTRACT [21 1 App] 309,196 Actuator for moving a diaphragm grid over photographic film during an X-ray exposure to screen secondary radiations from the film, comprising a drive shaft having thereon a pair of [52] US. Cl ..250/62, 250/93 coextensive intersecting helical grooves of opposite hand [51 1 Int. Cl. ..G03b 41/16 which merge at their ends to fonn an endless track, a follower [58] Field of Search ..242/84.4 Z; 74/424.8; 250/62, on the grid engaged in said track, and means for rotating said 250/63, 93 shaft for reciprocating said follower along saidtrack thereby to move said grid over the film. 56 R f C't d 1 e erences I e 9 Claims, 5 Drawing Figures UNITED STATES PATENTS 1,282,990 10/1918 Flegel ..242/84.42

5:12 11; ;-I- QZZ I J 43 2 470 I T "2] "J 1 ln 0: Q l 0 0 p2 Ewan/i o I 1 2a l I, I 22 Z6 94 ii i UJJMJ ACTUATOR FOR BUCKY DIAPHRAGMS Ancillary features include control means for causing the drive shaft to effect one complete reciprocation of the grid upon each actuation thereof, for delaying initiation of the X- ray exposure until the grid is moving, for usually moving the grid in one direction only during the exposure and thereafter returning it to its starting position, and for causing the grid to assume a starting position from which it can move substantially instantaneously upon initiation of rotation of the drive shaft.

Other features and advantages of the invention will become apparent from the drawings and the following description which are given for the purpose of acquainting those skilled in the art with the best mode presently contemplated by us for carrying out our invention.

THE DRAWINGS FIG. 1 is a plan view of a Bucky diaphragm embodying the actuator of this invention;

FIG. 2 is a cross-sectional view taken substantiallyon line 22 of FIG. 1;

FIG. 3 is a plan view, on a substantially enlarged scale, of the actuator;

FIG. 4 is a sectional view taken substantially on line 4-4 of FIG. 3; and

FIG. 5 is a schematic diagram of the electrical circuit of the actuator. A

DESCRIPTION Referring to FIGS. 1 and 2, we have shown our actuator as associated with a conventional X-ray diaphragm grid having a conventional box-like supporting frame 12. The grid is a well known component of X-ray equipment and part of what is commonly called a Bucky diaphragm. Its purpose is to prevent exposure of the X-ray film or plate to secondary radiations that would blur or obscure the image to be produced on the plate; and it is moved during the exposure so that it will not cast shadows on the plate. A more detailed explanation of Bucky diaphragms can be found in US. Pat. No. 2,591,536.

According to the present invention, the grid 10 is mounted for reciprocation on a pair of elongate anti-friction slides 14 disposed adjacent the opposite sides of the grid. As shown in FIG. 4, each slide comprises a supporting bracket 15 secured to the frame 12, a base track member 16 mounted on the bracket and having oppositely facing generally cylindrical edge portions, an inverted U-shaped track member 17 secured to the lower surface of the grid and having semi-cylindrical edge portions juxtaposed to the edge portions of the member 16, and a series of ball bearings 18 between each of the juxtaposed pairs of semi-cylindrical portions for slidably mounting the grid 10 on its frame 12. By virtue of the ball bearings and the elongate tracks, the grid is firmly supported for smooth rolling movement with little if any frictional resistance.

As shown in FIG. 1, an opening is provided within the frame 12 to one side of the grid for mounting the actuator of our invention, which actuator is indicated generally at 20. The actuator is comprised of an electric drive motor 21, preferably a gear motor, a drive shaft 22, a pair of microswitches 23 and 24 and an electric circuit, a few components which are indicated at 25, all mounted on the frame 12 to one side of the grid 10; and a follower 30 secured to the grid and engaged with the shaft 22.

The motor 21, shaft 22 and switch 24 are all mounted on a U-shaped bracket 26 secured to the frame 12 in such position that the shaft 22 is joumalled on its axis in spaced parallel rela- 1 tion to said slides. Intermediate its ends, the shaft is provided with a pair of coextensive intersecting helical grooves 27 and 28 which are merged at their ends to form an endless reciprocating track.

The follower 30 comprises a bracket 31 secured to the grid 10, a follower block 32 secured to the bracket 31 and encircling the shaft 22, a follower pin 33 in said block having a pointed or otherwise formed end for complementary engagement in the endless track 27-28 on the shaft, a spring 34 releasably biasing the pin into the track, and a mounting and adjusting screw 35 for the spring.

When the shaft 22 is rotated in one direction, one of the grooves, say the groove 27, comprises a screw thread for advancing the follower from one to the other end of the grooved part of the shaft. As the follower reaches the latter position, the pin 33 automatically and substantially immediately enters into the other groove 28, which because it is of opposite hand, automatically returns the follower from said other end to said one end of the grooved part of the shaft. Thus, upon rotation of the shaft in one direction only, the follower 30, and consequently the grid 10, will automatically reciprocate back and forth through a stroke equal to the length of the grooved part of the shaft.

In an X-ray machine, the grid movement must be nonsynchronous relative to the X-ray emission in order to attain a proper image on the film. Usually, the X-ray emission is at the rate of 120 pulses per second,and with a conventional Bucky diaphragm, we prefer a grid speed in the range of 0.845 to 0.875 inch per second to obtain a good X-ray picture without lines. The speed could be any multiple of the stated speed but higher speeds are usually disadvantageous because they tend to produce undesired vibrations, and lower speeds are difficult to maintain with any degree of precision. Thus, we prefer a speed of about 0.85 inch per second, and the motor and the grooves 27-28 are correlated to attain this result.

Also, at least for diagnostic X-rays, we prefer to move the grid in one direction only during exposure of the film further to insure a good clear picture. Accordingly, we make the grooved portion of the shaft 22 longer than the stroke required of the grid for usual or customary diagnostic exposures.

To insure that the full uni-directional stroke is available to the machine upon initiation of each X-ray, the switch 23 is provided for causing the motor to always drive the shaft in such manner as to bring the follower 30 and the grid 10 to a predetermined starting position wherein the follower pin 33 is engaged in the initial or starting part of the grid advancing groove 27. Specifically, as will become apparent from the following description of FIG. 5, whenever the motor is started, it will drive the shaft 22 for such period of time as to cause the grid to effect one complete reciprocation along the grooved part of the shaft, i.e., the full advance stroke and the full return stroke. As the grid is completing its return stroke, a pin 40 depending from the grid will engage the actuating arm 41 of the switch 23 to open the switch and stop the motor. By virtue of a short time delay built into the motor control, the grid and its follower will slightly overrun the end position of the return stroke so as to be positioned for instantaneous advancing movement upon the next energization of the motor.

To insure that the grid is moving before the X-ray is started, the switch 24 is provided as an X-ray circuit safety device. Like the switch 23, it is actuated to open circuit position by means of a pin 42 on the grid engaging the actuating arm 43 of the switch 24 throughout the vicinity of the starting position of the grid and its follower.

In view of the above description of the grid stopping switch 23, it will be appreciated that the grooved portion of the drive shaft 22 need be of a length no greater than about one-half the maximum movement required of the grid during an X-ray exposure. However, as above described, we prefer to make the grooved part of the shaft at least sufficiently long so that the grid will have only uni-directional movement, rather than reciprocatory movement, during most diagnostic X-ray exposures. Considering the present state of the art and the objectives above stated, we prefer to make the grooved part of the shaft about 1% inches long. With this length, at least percent of the X-rays usually taken will be taken in a single unidirectional stroke; partial reciprocatory return movement occurring in something less than 10 percent of the exposures.

Referring now to FIG. 5, the electrical circuitry of the motor 21 and the switches 23 and 24 is shown in the condition thereof when the grid and its follower are in starting position and an X-ray exposure is about to be initiated. As illustrated, the microswitches 23 and 24, both of which are normally closed switches, are at this time held in open circuit position by the pins 40 and 42 on the grid.

To initiate the taking of an X-ray, the operator will close a switch, which is usually a time exposure switch but here depicted simply as switch 50. When the switch is closed a circuit is completed from line B1 to line B4 through the coil 51c of a relay, thereupon closing two sets of contacts in the relay, namely, a motor start switch 51a and an X-ray start switch 51b.

The motor 21 is thereupon energized via power lines B1 and B4, the switch 51a, a rectifier 52 and a potentiometer 53 provided for the purpose of fine adjustment of the motor speed in accordance with the earlier description herein.

When the motor 21 and drive shaft 22 start to move the grid 10, the pins 40 and 42 are moved away from the switches 23 and 24 whereupon said switches close; the switch 24 then closing an X-raycontrol circuit comprised of lines B2 and B3, the X-ray start switch 51b and the X-ray microswitch 24.

Also at this time, the coil 54c of a holding relay is energized via line B2, the X-ray start switch 51b and the motor circuit to close a pair of relay contact sets comprising a relay-hold switch 54b and a motor-run switch 54a. When the motor microswitch 23 closes, the relay coil 540 is retained energized (irrespective of switch 51b) via B3, 541), 23, 54a and B4; and the motor 21 is retained energized (irrespective of switch 51a) via lines B3 and B4, and switches 23 and 54a. Consequently, when the Xray time cycle is complete and switch 50 opens, thereupon deenergizing coil 51c and opening the X-ray circuit via switch 51b, the fact that the switches 51a and 51b are open does not stop operation of the motor, which continues to run via the holding relay circuits until one reciprocation of the diaphragm is completed. Then, the switch 23 is opened (and also the switch 24) to open the circuit to its'initial condition and to stop the follower 30 and the grid in their initial starting positions.

From the foregoing, it should now be manifest that the invention provides a device of extreme simplicity and economy that nevertheless is a precision mechanism of great reliability. While we have shown and described what we regard to be the preferred embodiment of our invention, it is to be appreciated that various changes, rearrangements and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

We claim:

1. In an X-ray machine, in combination, a grid movable in a given path over photographic film during an X-ray exposure to screen secondary radiation from the film an electric motor, a drive shaft extending parallel to the path of grid movement connected to and rotated by said motor, said shaft having thereon a pair of co-extensive intersecting helical grooves of opposite hand which merge at their ends to form an endless track, and a follower on the grid engaged in said track, said motor when energized rotating said shaft and said shaft reciprocating said follower along said track and continuously moving said grid over the film without dwell times.

2. The apparatus of claim 1 wherein the length of the grooved part of the shaft is at least half as long as the maximum movement required of the grid during an X-ray exposure whereby the grid moves through no more than one complete reciprocation during an exposure, and control means actuated by the grid upon completion of said one reciprocation for stopping said motor and thus the grid at a predetermined starting position adjacent one end of the grooved part of said shaft.

3. The apparatus of claim 2 wherein one of said helical grooves advances said follower and the other returns it, and said motor is stopped when the follower has passed out of the return Tglroove and entered into the advance oove.

4. e apparatus of claim 3 wherein e length of the grooved part of the shaft is longer than the movement usually required of the grid during a diagnostic X-ray exposure, and one of said helical grooves advances the grid during the exposure and the other returns it usually after the exposure; control means actuated by the grid for stopping said motor when said follower passes out of the return groove and has entered into the advance groove, and control means for starting said motor upon initiation of each X-ray exposure.

5. The apparatus of claim 4 wherein the first named control means is a normally closed switch in series with said motor adapted to be opened by the grid when said follower passes out of the return groove and enters into said advance groove, the second named control means is a switch operatively as sociated with the X-ray means and connected in series with the motor in a circuit by-passing the first named switch, and a holding relay in circuit with said first named switch energized when said first named switch is closed for energizing said motor until said first named switch is opened by the grid.

6. The apparatus of claim 5 including an adjustable resistor in circuit with said motor for controlling the speed of grid movement.

7. In an X-ray machine, in combination, a grid movable over photographic film during an X-ray exposure to screen secondary radiation from the film, a grid supporting frame, a pair of spaced parallel elongate anti-friction slides on said frame slidably mounting the grid on the frame for reciprocatory movement, a rotary drive shaft joumalled on said frame parallel to said slides, said shaft having thereon a pair of co-extensive intersecting helical grooves of opposite hand which merge at their ends to form an endless track, a follower secured to the grid and engaged in said track, and an electric motor connected to said shaft for rotating said shaft, reciprocating said follower along said track and reciprocating the grid on said slides continuously without dwell times.

8. The apparatus of claim 7 wherein said shaft rotating means is an electric motor mounted on said frame and coupled to said shaft, said shaft and said motor having a normal starting position wherein said follower is disposed substantially at one end of the grooved part of said shaft, switch means operatively associated with the X-ray means for starting said motor, holding relay means energized subsequent to starting of said motor for maintaining the motor energized following completion of the X-ray exposure, and a normally closed switch in circuit with said relay means mounted on said frame to be actuated to open circuit position by the grid when the follower returns to its starting position, whereby the grid moves through one complete reciprocation each time the motor is started.

9. The apparatus of claim 8 including a second normally closed switch also actuated to open circuit position by the grid when the follower returns to its starting position, and means connecting said second switch in the circuit of the X-ray means for delaying initiation of the X-ray exposure until the grid is moving. 

1. In an X-ray machine, in combination, a grid movable in a given path over photographic film during an X-ray exposure to screen secondary radiation from the film, an electric motor, a drive shaft extending parallel to the path of grid movement connected to and rotated by said motor, said shaft having thereon a pair of co-extensive intersecting helical grooves of opposite hand which merge at their ends to form an endless track, and a follower on the grid engaged in said track, said motor when energized rotating said shaft and said shaft reciprocating said follower along said track and continuously moving said grid over the film without dwell times.
 2. The apparatus of claim 1 wherein the length of the grooved part of the shaft is at least half as long as the maximum movement required of the grid during an X-ray exposure whereby the grid moves through no more than one complete reciprocation during an exposure, and control means actuated by the grid upon completion of said one reciprocation for stopping said motor and thus the grid at a predetermined starting position adjacent one end of the grooved part of said shaft.
 3. The apparatus of claim 2 wherein one of said helical grooves advances said follower and the other returns it, and said motor is stopped when the follower has passed out of the return groove and entered into the advance groove.
 4. The apparatus of claim 3 wherein the length of the grooved part of the shaft is longer than the movement usually required of the grid during a diagnostic X-ray exposure, and one of said helical grooves advances the grid during the exposure and the other returns it usually after the exposure; control means actuated by the grid for stopping said motor when said follower passes out of the return groove and has entered into the advance groove, and control means for starting said motor upon initiation of each X-ray exposure.
 5. The apparatus of claim 4 wherein the first named control means is a normally closed switch in series with said motor adapted to be opened by the grid when said follower passes out of the return groove and enters into said advance groove, the second named control means is a switch operatively associated with the X-ray means and connected in series with the motor in a circuit by-passing the first named switch, and a holding relay in circuit with said first named switch energized when said first named switch is closed for energizing said motor until said first named switch is opened by the grid.
 6. The apparatus of claim 5 including an adjustable resistor in circuit with said motor for controlling the speed of grid movement.
 7. In an X-ray machine, in combination, a grid movable over photographic film during an X-ray exposure to screen secondary radiation from the film, a grid supporting frame, a pair of spaced parallel elongate anti-friction slides on said frame slidably mounting the grid on the frame for reciprocatory movement, a rotary drive shaft journalled on said frame parallel to said slides, said shaft having thereon a pair of co-extensive intersecting helical grooves of opposite hand which merge at their ends to form an endless track, a follower secured to the grid and engaged in said track, and an electric motor connected to said shaft for rotating said shaft, reciprocating said follower along said track and reciprocating the grid on said slides continuously without dwell times.
 8. The apparatus of claim 7 wherein said shaft rotating means is an electric motor mounted on said frame and coupled to said shaft, said shaft and said motor having a normal starting position wherein said follower is disposed substantially at one end of the grooved part of said shaft, switch means operatively associated with the X-ray means for starting said motor, holding relay means energized subsequent to starting of said motor for maintaining the motor energized following completion of the X-ray exposure, and a normallY closed switch in circuit with said relay means mounted on said frame to be actuated to open circuit position by the grid when the follower returns to its starting position, whereby the grid moves through one complete reciprocation each time the motor is started.
 9. The apparatus of claim 8 including a second normally closed switch also actuated to open circuit position by the grid when the follower returns to its starting position, and means connecting said second switch in the circuit of the X-ray means for delaying initiation of the X-ray exposure until the grid is moving. 